1. Field of the Invention
This invention relates to diamidophosphorothiolate urease inhibitors and urease inhibited urea based fertilizer compositions. More particularly, this invention relates to urease inhibited urea based fertilizer compositions which contain certain diamidophosphorothiolate compounds as the urease inhibitors, and to methods and compositions of inhibiting the catalytic activity of urease through application of such phosphorothiolate compounds to some plant growth media.
2. The Prior Art
It is well known in the art to use urea and urea compositions in fertilizers for application to the soil. The effective life of such fertilizers, however, is of short duration wherever microbiological activity exists in the soil to which the fertilizer is applied. This is due to the fact that urea is hydrolyzed rapidly, and nitrogen is lost in the form of ammonia, when urea is placed under or on the surface of soil which contains urease. Urease, a crystallizable enzyme occurring in numerous bacteria and fungi, as for example Micrococcus urease, catalyzes the conversion of urea into ammonia and carbon dioxide. The reactions are as follows: ##STR1## A portion of the ammonia thus formed is held by absorbing constituents of the soil and is available to plants as nutrient. However, a large amount of the ammonia may be lost to the air. A further problem resulting from the action of urease is that the accumulation of ammonium in the soil may cause damage to germinating seedlings and young plants.
One approach to reduction of problems resulting from the activity of soil urease toward soil applied urea is to find compounds that inhibit urease activity when applied to soils in conjunction with fertilizer urea. This approach has received considerable attention, and several classes of compounds have been used as urease inhibitors.
For example, some prior art describes various phosphoro compounds which are useful as urease inhibitors. Illustrative of such prior art are East German Pat. Nos. 142,714, 212,026, 122,177, 122,621 and 130,936 and Great Britain Pat. No. 1,494,774 which describe various phosphorodiamidate compounds as urease inhibitors. U.S. Pat. No. 4,242,325 describes a method of controlling the enzymatic decomposition of urea to ammonia and carbonic acid due to the action of urease, which method comprises exposing the enzyme to certain phosphoric triamide compounds. U.S. Pat. No. 4,182,881 describes the use of certain N-(diaminophosphinyl)arylcarboxyamide compounds as inhibitors of the enzyme urease in the urinary tract. U.S. Pat. No. 4,225,526 desribes the use of 8-[(4-aminophenyl)-sulfonyl]amino-2-napthalenyl phosphorodiamidate compounds as inhibitors of the enzyme urease, and U.S. Pat. No. 4,222,948 describes the use of ([(4-aminophenyl)sulfonyl]amino)phenyl phosphorodimidates as inhibitors of the enzyme urease.
Still other prior art describes the use of certain phosphoric triamide compounds for other purposes. For example, Great Britain Pat. No. 830,800 describes certain phosphoric triamide compounds which are useful as flame proofing agents.